Premature infants face a host of unique issues due to their developmental immaturity. One of the most devastating is necrotizing enterocolitis (NEC), which yearly kills 12 babies per 100,000 live births in the US and frequently leaves survivors with severe feeding issues, liver failure, and neurodevelopmental disability. Understanding mechanisms of intestinal injury and repair in developing intestine is key to developing new prevention and therapeutic strategies for NEC. This proposal will investigate the mechanisms of gastrointestinal epithelial cell injury and repair during development by testing the hypothesis that the intestine of premature infants and newborn mice is more susceptible to TNF-induced injury because of an ontogenically normal decrease in expression and activation of EGFR. This hypothesis will be examined through the following specific Aims: 1) Define the effects of TNF on intestinal injury and apoptosis at different developmental stages. This will be accomplished using histopathologic injury scores of early intestinal damage as well as immunofluorescence and immunohistochemical assays for apoptosis;2) Determine the effects of TNF on EGFR inhibition in neonates compared to adults. We will study the effects of TNF on multiple EGFR phosphorylation sites and down-stream targets, and the role of EGFR internalization in TNF-stimulated EGFR inhibition. This aim will utilize immunofluorescence and western blot analysis to study the down-stream targets of EGFR activation;and 3) Determine the role of EGFR activation in protecting against TNF induced injury using pharmacologic and genetic models of EGFR activation. This aim will build on techniques developed in Aim 1 and 2 and apply them to mice with constitutively active EGFR, pharmacologically active EGFR, and deficiency of EGFR. Overall, these studies will reveal the roles of TNF and EGFR in intestinal injury processes in developing intestinal tissue, and will identify potential novel avenues of therapy and chemoprevention. In addition to the above studies, this proposal will greatly enhance career development through didactic training in cell biology, developmental biology, and statistics;by providing mentoring from a strong laboratory;and by utilizing the strong resources uniquely available at Vanderbilt to foster independent investigation in gastrointestinal disease.